24 outpatient children ages 7-17 who are suffering from an anxiety disorder (Separation-anxiety, overanxious disorder, PTSD) will be given two challenge drugs, p.o. fenfluramine or iv clonidine. These challenge drugs will be used to stimulate neurohormonal output which will characterize the neurobiology of this condition in children. These patients will be compared to 12 normal age/sex matched controls. Outcome variables will be area under the time-plasma concentration curve for growth hormone, cortisol prolactin and ACTH.